Outstanding gathering student pub set up fast (7)
I believe the answer is:
durable
'fast' is the definition.
(thesaurus)
'outstanding gathering student pub set up' is the wordplay.
'outstanding' becomes 'due' (an outstanding debt is due).
'gathering' is an insertion indicator (gather can mean to acquire or bring in).
'student' becomes 'L' (as in L-plates for learner drivers).
'pub' becomes 'bar' (both are drinking establishments).
'set up' says the letters should be written in reverse (in a down clue, letters go up).
'l'+'bar'='lbar'
'lbar' in reverse letter order is 'rabl'.
'due' going around 'rabl' is 'DURABLE'.
(Other definitions for durable that I've seen before include "Lasting a long time" , "Tough and long-wearing" , "Made to last" , "Hardy" , "Firm" .)